coal classification

 any of various ways in which coal is grouped. Most classifications are based on the results of chemical analyses and physical tests, but some are more empirical in nature. Coal classifications are important because they provide valuable information to commercial users (e.g., for power generation and coke manufacturing) and to researchers studying the origin of coal.

      The most common classification is based on rank, referring to the degree of coalification that has occurred. The rank of a coal is determined primarily by the depth of burial and temperature to which the coal was subjected over time. With increasing temperature, peat is converted to lignite, a very soft, low-rank coal. With further increases in temperature, lignite is transformed into subbituminous coal and then into bituminous coal. At even higher temperatures, usually accompanied by intense deformation generated by the folding and faulting of the Earth's crust, anthracites (anthracite), the highest rank of coal, are produced. The increase in coal rank is accompanied by increases in the amount of fixed carbon and by decreases in the amount of moisture and other volatile material in the coal. In general, the calorific (heat) value of coal increases with rank from lignite through bituminous coal. In addition, the terms used for various coal ranks vary from country to country.

      Coal may be classified in rock types (or lithotypes) based on the presence of petrological components known as macerals (maceral). Based on maceral content and its appearance in a hand specimen, coal is classified into four principal types: clarain, durain, fusain, and vitrain.

      Coal may also be classified in grades using subjective terms (e.g., “low-sulfur coal,” “high-ash coal”) with reference to their impurities for commercial purposes.

Otto C. Kopp
 

* * *


Universalium. 2010.

Look at other dictionaries:

  • Coal Classification —   In the United States, coals are classified by rank progressively from lignite (least carbonaceous) to anthracite (most carbonaceous) based on the proximate analyses of various properties (fixed carbon, volatile matter, heating value, and… …   Energy terms

  • coal — coalless, adj. /kohl/, n. 1. a black or dark brown combustible mineral substance consisting of carbonized vegetable matter, used as a fuel. Cf. anthracite, bituminous coal, lignite. 2. a piece of glowing, charred, or burned wood or other… …   Universalium

  • coal — n a brown to black combustible sedimentary rock (in the geological sense) composed principally of consolidated and chemically altered plant remains. DISCUSSION Conditions required for formation of coal are believed to include accumulation of… …   Coke&Coal Terminology

  • Coal — Sedimentary Rock Anthracite coal Composition Primary carbon Secondary hydrogen, sulfur …   Wikipedia

  • Coal Tit — Adult British Coal Tit, P. a. britannicus (note greenish grey back) Conservation status …   Wikipedia

  • Coal Skink — Conservation status Least Concern (IUCN 3.1) …   Wikipedia

  • Coal Run (novel) — Coal Run   Author(s) Tawni O’Dell Countr …   Wikipedia

  • Coal-crested Finch — Conservation status Near Threatened (IUCN 3.1) Scientific classification K …   Wikipedia

  • coal utilization — Introduction        combustion of coal or its conversion into useful solid, gaseous, and liquid products. By far the most important use of coal is in combustion, mainly to provide heat to the boilers of electric power plants. Metallurgical coke… …   Universalium

  • Coal grade —   This classification refers to coal quality and use.   • Briquettes are made from compressed coal dust, with or without a binding agent such as asphalt.   • Cleaned coal or prepared coal has been processed to reduce the amount of impurities… …   Energy terms

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.